Better surfacing of extensions documentation: github not enough

[corneliusroemer]

I've had the same feeling as expressed by @MichaelWest22 in a comment on a different issue re v1 search results being shown for v2 search.

If v1 results are dropped for v2, then extensions will not return results. There should be better surfacing of extensions that isn't under v1.

Also there is almost no useful information in extensions.htmx.org. one of the core issues is that all the websocket and sse documentation only exists in the v1 old site as all this documentation was removed with v2 and moved into the extensions git repo as .md files. But these are just not well indexed or easy to search in github. The extensions site was turned into a single vanilla html file only that just links to github with one sentence per extension. Trying to convert the extensions repo into a proper searchable documentation website via Zola like the core htmx repo uses is a lot of effort. Also there seems to be very little searchable content left about extensions on the htmx.org site now. Would be nice if there was some pages in the main htmx documentation site for common things like extensions, sse and websockets that are going to be highly searched terms that used to resolve well in v1 site.

Originally posted by @MichaelWest22 in #2813 (comment)